No “Link between herpes in pregnancy and autism”

You may have read some headlines in the Sun or the Mail, etc. They report “‘Women infected with herpes while they are pregnant are twice as likely to have a child with autism.” This headline comes from a study looking at whether maternal infections during pregnancy are associated with the risk of neurological developmental disorders such as autism spectrum disorders (ASDs).
However, these scare stories refer to one small area of the findings. In fact, the report was not able to confirm the association between maternal infections and autism in children. The suggestion that herpes simplex infection is a risk factor for autism was based on just 14 women, so it not reliable.

The Norwegian study looked at levels of antibodies to five different infections in pregnant women. They checked samples at 18 weeks during pregnancy and after delivery. These antibodies would indicate current or previous infection or immunity following vaccination. Researchers then followed up whether any of the women had children later diagnosed with autism.

Herpes virus, given colour to make it look pretty.

They looked at levels of antibodies to rubella (German measles), toxoplasma gondii (a parasite found in cat poo) and three of the herpes family of viruses: HSV-1 and HSV-2 and cytomegalovirus (which causes a glandular fever-like illness).

The study initially found no association between any of the levels of antibodies during pregnancy or after delivery, and the development of ASD in boys or girls. So they performed numerous additional analyses. Finally, they were able to say that high levels of antibodies to the HSV-2 virus during mid-pregnancy were associated with the development of ASD in boys. However, this was based on just 14 women so it not reliable.

NHS Choices

NHS Choices reports that “Both The Sun and the Mail Online are arguably guilty of scaremongering and inaccuracy in their reporting of the study. They did not point out any of the limitations of the study, in particular that the results are based on such a small number of women that the results could have been down to chance.”

“In contrast, CNN provides useful contrasting opinions from independent experts. Its coverage includes a quote from Dr David Winston Kimberlin, a professor of paediatric infectious diseases. He says “pregnant women should not be worried about HSV-2 (genital herpes) as a cause of autism based upon the findings of this single exploratory research study”.”

This finding has been widely reported in the media – because it includes the word ‘herpes’. However, the conclusion is not reliable since it is based on just 14 women. Performing repeated unplanned analyses is bound to come up with some association in the end through sheer chance.